The IEEE 802.1aq standard (also referred to 802.1aq hereinafter), was published in 2012 and defines a routing solution for Ethernet that replaces prior routing solutions including Spanning Tree Protocols. 802.1aq is also known as Shortest Path Bridging or SPB. 802.1aq enables the creation of logical Ethernet networks on native Ethernet infrastructures. 802.1aq employs a link state protocol (i.e., Intermediate System to Intermediate System (IS-IS)) to advertise network topology and logical network membership of the nodes in the network. The link state information is used to calculate shortest path trees from all bridges in the SPB region. The computations are done in an independent and distributed manner with each node generating its own forwarding tables to implement its part in SPB region wide forwarding.
Data are encapsulated at the edge nodes of the networks implementing 802.1aq. This encapsulation can be in 802.1ah or tagged 802.1Q/p802.1ad frames. These frames are transported only to other members of the respective logical network. Unicast and multicast are also supported by 802.1aq. All such routing is done via symmetric shortest paths. Multiple equal cost shortest paths are supported. Implementation of 802.1aq in a network simplifies the creation and configuration of the various types of networks including provider networks, enterprise networks and cloud networks. The configuration is comparatively simplified and diminishes the likelihood of error, specifically human configuration errors in comparison with prior routing solutions. 802.1aq also increases bandwidth and reliability by improved use of the network mesh topology. By enabling all paths greater utilization can be obtained through the use of multiple equal cost paths. Improved convergence times and larger topologies can also be supported.
EVPN is a new approach to doing L2VPNs over MPLS using the BGP protocol. It offers a number of improvements over previous L2 VPN technologies, a principal one being the use of the BGP control plane for mirroring the Ethernet FDBs across the set of supporting MPLS PEs.